rust/tests/ui/macros/concat.rs

fn main() {
    concat!(b'f');  //~ ERROR: cannot concatenate a byte string literal
    concat!(b"foo");  //~ ERROR: cannot concatenate a byte string literal
    concat!(foo);   //~ ERROR: expected a literal
    concat!(foo()); //~ ERROR: expected a literal
}
Implement a concat!() format extension This extension can be used to concatenate string literals at compile time. C has this useful ability when placing string literals lexically next to one another, but this needs to be handled at the syntax extension level to recursively expand macros. The major use case for this is something like: macro_rules! mylog( ($fmt:expr $($arg:tt)) => { error2!(concat!(file!(), ":", line!(), " - ", $fmt) $($arg)); }) Where the mylog macro will automatically prepend the filename/line number to the beginning of every log message. 2013-10-06 04:15:46 +00:00			`fn main() {`
Use consistent terminology for byte string literals Avoid confusion with binary integer literals and binary operator expressions in libsyntax 2015-09-03 07:54:53 +00:00			`concat!(b'f'); //~ ERROR: cannot concatenate a byte string literal`
			`concat!(b"foo"); //~ ERROR: cannot concatenate a byte string literal`
Implement a concat!() format extension This extension can be used to concatenate string literals at compile time. C has this useful ability when placing string literals lexically next to one another, but this needs to be handled at the syntax extension level to recursively expand macros. The major use case for this is something like: macro_rules! mylog( ($fmt:expr $($arg:tt)) => { error2!(concat!(file!(), ":", line!(), " - ", $fmt) $($arg)); }) Where the mylog macro will automatically prepend the filename/line number to the beginning of every log message. 2013-10-06 04:15:46 +00:00			`concat!(foo); //~ ERROR: expected a literal`
			`concat!(foo()); //~ ERROR: expected a literal`
			`}`